(A) MBP immunolabeling of sciatic nerve sections showing delayed loss of myelin in –null nerves compared with controls, 3 d after transection of nerves of 5-d-old mice

Bar, 10 μm. (B) Quantification of the delay in myelin disappearance by quantitative image analysis of MBP-immunolabeled sections (comparable to those shown in A) 2, 3, and 5 d after injury (expressed as percentage of MPB area in uncut P5 nerve). In every case, the difference between c-Jun–null and control nerves is significant (P < 0.01). (C) Electron micrographs showing –null and control nerves from 5-d-old mice, intact and 3 d after injury as indicated. Note preservation of rounded or partially collapsed myelin sheaths in –null nerves. Bar, 4 μm. (D) Counts of myelin sheaths (rounded or collapsed) in c–null and control nerves 3 and 5 d after injury (3 d, P < 0.05; 5 d, P < 0.01). Error bars show standard deviation of the mean.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A) Western blot showing that MKK7, presumably by activating JNK, inhibits Krox-20–induced myelin protein expression

The cells were coinfected with adenoviruses expressing the constructs indicated. (B) Western blot of cells infected with adenoviruses expressing control LacZ or activated MKK7 to activate JNK. Note that periaxin induced by 2 d of exposure to 1 mM of db-cAMP in LacZ control cells is inhibited by MKK7 expression. (C–F) MKK7 activates c-Jun even in the presence of Krox-20. C and E show that Krox-20 coinfected with a control LacZ-expressing adenovirus suppresses c-Jun levels. D and F show that when Krox-20 is coexpressed with MKK7, high c-Jun levels are maintained. (G) MKK7-mediated suppression of myelin gene expression depends on c-Jun. In normal cells ( con), Krox-20–induced periaxin expression (K20/LacZ) is suppressed by MKK7 (K20/MKK7). This suppression does not occur when this experiment is repeated in cells without c-Jun ( null). Error bars show one standard deviation of the mean. (H–K) Reactivation of JNK/c-Jun in Krox-20–expressing cells that already synthesize P abolishes P protein expression. Retrovirally infected cells already expressing Krox-20 and P were infected with either LacZ control (H and I) or MKK7-expressing (J and K) adenoviruses. Cells were labeled with either LacZ and P (H and I) or MKK7 and P (J and K) antibodies. Note down-regulation of P protein in Krox-20–expressing cells infected with MKK7 adenovirus. Bars, 15 μm.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A and B) Cells cotransfected with empty GFP vector (to visualize transfected cells) and an empty control vector (EV; A) or a vector (B)

Both cultures were then treated with 1 mM db-cAMP for 2 d to induce Krox-20 and were immunolabeled for Krox-20. In A, arrows point to induced Krox-20 in nuclei of GFP-positive control cells (yellow nuclei of Krox-20–positive GFP-positive cells). In B, no Krox-20 is induced (arrows) in cells containing . Arrowheads in both panels indicate untransfected cells that have been induced to express Krox-20 by db-cAMP as controls for induction. (C) Activation of JNK inhibits induction of Krox-20. Western blot of cells infected with adenovirus expressing control LacZ or virus expressing activated MKK7 to activate JNK is shown. Note that the Krox-20 and periaxin induced by 2 d of exposure to 1 mM db-cAMP in LacZ control cells is inhibited by MKK7 expression. Note also that MKK7 elevates c-Jun in the presence of db-cAMP. (D–G) In –null cells, loss of Krox-20 expression is significantly delayed. Double immunolabeling of control cells (D and E) and –null cells (F and G) for Krox-20 (red) and periaxin (green) after 2 d in culture in DM containing 20 ng/ml NRG-1 is shown. Note that Krox-20 has disappeared from the control cells, whereas many –null cells still have Krox-20–positive nuclei (G, arrows). Note that –null Krox-20–positive cells are also periaxin positive (F, arrows), whereas control cells have lost periaxin expression (D). Bars, 15 μm.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A) Western blot showing that c-Jun is absent from cells infected with CRE-expressing adenovirus

The blot also compares periaxin in control (Con) and –null cells (CRE) infected with GFP control adenovirus (GFP) or a Krox-20/GFP virus (K20). Note high periaxin levels in Krox-20–infected –null cells (CRE). (B–E) control ( con) and –null mouse Schwann cells 2 d after infection with Krox-20/GFP adenovirus. Note that Krox-20 induces much higher levels of P protein in –null cells (D and E) than in control cells (B and C). The reason why P levels in the Krox-20–expressing control cells appear low in this picture (C) compared with other comparable experiments (e.g., ) is that exposure had to be reduced (equally for C and E) to avoid overexposure in E. (F and G) P protein expression in control cells P ( con) and c–null mouse Schwann cells after 3 d of exposure to db-cAMP/NRG-1. Note that cAMP/NRG-1 induces substantially higher P levels in cells without c-Jun. Bars, 15 μm.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A and B) Cotransfection of Krox-20/GFP with Jun(Asp) or with Jun(Ala) inhibits Krox-20–mediated induction of periaxin and P

K20/EV represents cells cotransfected with Krox-20 and control vector. (C–F) P in situ experiment showing that cotransfection of Krox-20/GFP with Jun(Ala) inhibits Krox-20–mediated induction of mRNA. C and D are controls, and the arrows show a cell coexpressing Krox-20 and a control vector where Krox-20 has induced P mRNA. Arrows in E and F show a cell coexpressing Krox-20 and Jun(Ala) where Jun(Ala) has inhibited Krox-induced expression. Bar, 15 μm. (G) Percentages of GFP-positive cells that also express mRNA in cells cotransfected with the constructs indicated. Error bars show one standard deviation of the mean.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p